1. Field of the Invention
This invention relates to engine control for improved fuel efficiency, and more specifically to fuel economy benefits achieved largely through refinement of automatic transmissions currently used in automotive applications.
2. Description of the Prior Art
Current production cars with automatic transmissions have several short comings with regard to fuel economy. Most notable among these is energy dissipated as heat in the transmission torque converter due to the fact that converter lockup clutch engagement often does not occur during city driving until vehicle acceleration is essentially complete.
Another major problem concerns the modern engine designs which achieve an unusually good combination of performance and fuel economy by producing high power output relative to piston displacement. Such high specific output engines are only rarely available with automatic transmissions, in no small part because the high torque converter stall speeds desirable with high specific output engines exacerbate converter overheating. In addition, an extra forward speed ratio would much improve the results achieved using automatic transmissions in conjunction with high specific output engines.